The present invention refers to a composite manufacturing method and device to be applied in composite part manufacturing processes. It might apply to both structural parts, such as ribs, and parts where both tight tolerances and excellent structural behavior are required, such as fittings.
Current composite material curing processes require the combined effort of pressure and temperature to ensure the quality of the final part. The combination of both factors takes place in autoclaves or ovens.
A curing process generally needs pressure, debulking and a high temperature. Pressure is needed to ensure a correct distribution of the resin and good compaction between the prepreg layers in the workpiece. Debulking is needed to draw air from the workpiece to obtain good compaction and avoid porosity. Temperature is needed to polymerize the resin because firstly the resin becomes liquid and is distributed through the mold and then it begins to polymerize until it gets hard.
Epoxy prepreg materials, which present excellent mechanical properties, require pressure and temperature to be shaped and cured and they are used to obtain all sorts of aeronautical parts, ranging from fittings to aerodynamic surfaces. Therefore, manufacturing an epoxy part requires a big amount of energy and gas. The final acceptance of the part depends on its structural integrity, which is evaluated in terms of porosity levels and it also depends on its fit to the dimensional and geometrical tolerances defined for said element. Integrity is deeply dependent on the process parameters, time, pressure, vacuum, material, etc., while geometry is concerned by several factors such as tooling, stacking sequence and also the kind of material used.
Ovens, on the other hand, are normally used in processes where pressure is applied by injection equipment, such as Resin Transfer Moulding (RTM) or Liquid Resin Infusion (LRI). Those injection processes compensate the normally lower levels of injection pressure when compared to standard autoclave cycles with higher levels of vacuum. Although RTM parts present worst mechanical behavior than those made out of prepregs in autoclaves, an RTM process provides parts with tighter geometrical tolerances that makes RTM an ideal technology to manufacture parts with geometrical assembly requirements.
There are processes, such as Same Qualified Resin Transfer Moulding (SQRTM), that combines the benefits of RTM regarding tight tolerances and prepreg regarding mechanical properties, although they still require the presence of both temperature and pressure that implies the use of costly equipment.